1. Field of the Invention
The present invention relates to an apparatus and method for integrating a background pattern image into an input image.
2. Description of the Related Art
In order to deter unauthorized copying of a document image depicted on the original paper, a technique has been employed in which a character string such as “copy” is printed onto paper as a background pattern image together with the document image.
Such a “background pattern image” consists of many character dots 6J and dots-to-be-invisible 6S as shown in FIG. 5. The character dots 6J represent a character string, and the dots-to-be-invisible 6S camouflage (disguise) the character string.
Each of the character dots 6J and the dots-to-be-invisible 6S is very small. While the character dot 6J has a size that can be scanned by a scanner, the dot-to-be-invisible 6S has a size that cannot be scanned thereby. Accordingly, if a copier is used to copy the document image depicted on the original paper, only the character dots 6J are printed on paper with the dots-to-be-invisible 6S not printed thereon. This makes the character string represented by the background pattern image apparent. It is, thus, possible to deter someone from making unauthorized copying.
Overlaying a background pattern image on a document image sometimes renders the document itself illegible. To cope with this, there has been proposed the following method.
In combining character data and modification data that are stored separately from each other, and outputting the resultant data, a CPU determines whether or not the character data or the modification data is present. Note that background pattern image data is used as the modification data. When both the character data and the modification data to be outputted are present, a further determination is made as to whether or not the modification data exceeds a prescribed density. Then, when it is determined that the modification data exceeds the prescribed density, trimming is performed in which a portion corresponding to one dot adjacent to a character dot of the character data is turned OFF, and then, the character data is combined with the modification data and the resultant data is outputted (Japanese Laid-open Patent Publication No. 8-180047).
FIGS. 10A to 10C are diagrams showing an example of a Quick Response (QR) code.
According to the method described in Japanese Laid-open Patent Publication No. 8-180047, characters are reversed, and therefore, a background pattern image is less camouflaged.
Further, the method described in Japanese Laid-open Patent Publication No. 8-180047 is not applicable to an object other than characters, for example, not applicable to a QR code as shown in FIG. 10A. This is because if dots constituting the QR code are reversed, it becomes impossible for a computer to analyze the QR code.
As shown in FIG. 10B, simply overlaying a background pattern image on the QR code again makes it difficult for a computer to analyze the QR code. To cope with this, it may be conceived that a background pattern image is disposed so as not to overlap with the QR code and its periphery as shown in FIG. 10C. This, however, makes the QR code stand out for the entire document.